644767680567 has 4 divisors (see below), whose sum is σ = 859690240760. Its totient is φ = 429845120376.

The previous prime is 644767680563. The next prime is 644767680569. The reversal of 644767680567 is 765086767446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644767680567 - 2² = 644767680563 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644767680498 and 644767680507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644767680563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107461280092 + ... + 107461280097.

It is an arithmetic number, because the mean of its divisors is an integer number (214922560190).

Almost surely, 2^644767680567 is an apocalyptic number.

644767680567 is a deficient number, since it is larger than the sum of its proper divisors (214922560193).

644767680567 is a wasteful number, since it uses less digits than its factorization.

644767680567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214922560192.

The product of its (nonzero) digits is 284497920, while the sum is 66.

The spelling of 644767680567 in words is "six hundred forty-four billion, seven hundred sixty-seven million, six hundred eighty thousand, five hundred sixty-seven".